Carmax pays the true wholesale price for the car. No one would sell them their cars for half the value. You have to look at trade in value to determine what your car is worth, not retail.
Same happened to me. So I Google Kelly Blue Book dealers. You input your vehicle info with pictures and a quote is emailed to you. I took that quote to a dealer listed on the email and they gave me 400 more on top of KBB value! It was a Ford Escape on its last leg with dents and they were a Toyota dealership. Word of advice: go toward the end of the month when reps need to make their commission quotas. ;)
I say you're beat bet is to get the quote from carmax and shop around with that quote in hand.
Carmax is the only place that will buy your car without selling you a new one. You have to consider what you would actually get for the car somewhere else. Trade in value is minimal at most other dealers. They may offer you more, but they always have an angle. They move the numbers around to make it look like you got more for the trade in, but you have to look at the bottom line. They never give you what they're selling the same car for. Selling it yourself can be tough. A lot of lowballers out there. Carmax is straightforward and the cash is in your hand.
Thanks! Your answer is awaiting moderation.